When the SS Gairsoppa was torpedoed by a German U-boat, it took its huge silver cargo to a watery grave. Seventy years later, US divers said they are working to recover what may well be the biggest shipwreck haul ever. Florida-based Odyssey Marine Exploration on Monday confirmed the identity and location of the Gairsoppa and cited official documents indicating the ship was carrying some 219 tons of silver coins and bullion when it sank in 1941 in the North Atlantic some 490km off the Irish coast. That's worth about $200m today, which would make it history's largest recovery of precious metals lost at sea, Odyssey said. "We've accomplished the first phase of this project -- the location and identification of the target shipwreck - and now we're hard at work planning for the recovery phase," Odyssey senior project manager Andrew Craig said in a statement. "Given the orientation and condition of the shipwreck, we are extremely confident that our planned salvage operation will be well suited for the recovery of this silver cargo." Recovery is expected to begin next spring. After a tender process the British government awarded Odyssey an exclusive salvage contract for the cargo, and under the agreement Odyssey will retain 80% of the silver bullion salvaged from the wreck. The 125m Gairsoppa had been sailing from India back to Britain in February 1941, and was in a convoy of ships when a storm hit. Running low on fuel, the Gairsoppa broke off from the convoy and set a course for Galway, Ireland. It never made it, succumbing to a U-boat's torpedo in the contested waters of the North Atlantic. Of the 85 people on board, only one survived. The Gairsoppa came to rest nearly 4 700m below the surface, but Odyssey is insisting that won't prevent a full cargo recovery. "We were fortunate to find the shipwreck sitting upright, with the holds open and easily accessible," Odyssey chief executive Greg Stemm said. "This should enable us to unload cargo through the hatches as would happen with a floating ship alongside a cargo terminal." Odyssey, a world leader in deep-ocean exploration, recently conducted remotely operated vehicles from its main ship, the Odyssey Explorer, to inspect the shipwreck. It said it acquired still and video imagery from the site which were used to confirm the identify and evaluate the condition of the Gairsoppa.